6-4 a. Calculate the amount of depreciation expense for one year for the build-ings and improvements listed below if the buildings have an average estimated life of 20 years and the improvements have an average estimated life of 10 years with no salvage value. Use the straight-line method. Buildings: Cost = $125,000 Improvements: Cost $62,500 b. Use the activity method and calculate depreciation expense on the Farmers' truck for 20x2 and 20X3. They drove the truck 24,500 miles in 20x2 and 22,600 miles in 20X3